Osteoarthritis is a type of arthritis that is
caused by breakdown of cartilage, with the eventual loss of the cartilage of the
joints. Cartilage is a protein substance that serves as a "cushion"
between the bones of the joints. Osteoarthritis is also known as degenerative
arthritis. Among the over 100 different types of arthritis conditions,
osteoarthritis is the most common and affects over 15 million people in the
United States. Before age 45, osteoarthritis occurs more frequently in males.
After age 55, it occurs more frequently in females. In the United States, all
races appear to be equally affected. A higher incidence of osteoarthritis exists
in the Japanese population, while South African blacks, East Indians, and
southern Chinese have lower rates. Osteoarthritis usually affects the hands,
feet, spine, and the large weight-bearing joints, such as the hips and knees.